Selective Deposition Of Aluminum Oxide On Metal Surfaces

ABSTRACT

Processing methods for depositing aluminum etch stop layers comprise positioning a substrate within a processing chamber, wherein the substrate comprises a metal surface and a dielectric surface; exposing the substrate to an aluminum precursor gas comprising an isopropoxide based aluminum precursor to selectively form an aluminum oxide (AlOx) etch stop layer onto the metal surface while leaving exposed the dielectric surface during a chemical vapor deposition process. The metal surfaces may be copper, cobalt, or tungsten.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/814,863, filed Nov. 16, 2017, which claims priority to U.S.Provisional Application No. 62/426,030, filed Nov. 23, 2016, the entiredisclosures of which are hereby incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to methods of depositing thinfilms. In particular, the disclosure relates to methods of selectivelydepositing aluminum oxide layers as etch stop layers on metal surfaces.

BACKGROUND

Integrated circuits are made possible by processes that produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods for bothdeposition of desired materials and removal of exposed material.Selectively depositing a film on one surface relative to a differentsurface is useful for patterning and other applications.

During etch steps to preferentially remove dielectric material, metalsurfaces are protected with an etch stop layer. Further oxidation of themetal surfaces is to be minimized. An exemplary etch stop layer isaluminum oxide (AlOx). Previous processes rely on physical vapordeposition (PVD) of AlOx.

Node sizes continue to decrease, e.g., from 10 nm to 5-7 nm.

There is a continuing need for methods that efficiently and effectivelydeposit AlOx as etch layers as node sizes decrease.

SUMMARY

One or more embodiments of the disclosure are directed to processingmethods comprising positioning a substrate within a processing chamber,the substrate comprising a metal surface and a dielectric surface. Thesubstrate is exposed to an aluminum precursor gas comprising anisopropoxide based aluminum precursor and a non-oxidizing reactant toform an aluminum oxide (AlOx) etch stop layer on the metal surface.

Additional embodiments of the disclosure are directed to processingmethods comprising positioning a substrate within a processing chamber,wherein the substrate comprises a metal surface and a dielectricsurface. The substrate is exposed to a first process conditioncomprising an aluminum precursor gas comprising an isopropoxide basedaluminum precursor. The substrate is exposed to a second processcondition comprising a reactant to selectively form an aluminum oxide(AlOx) etch stop layer onto the metal surface while leaving exposed thedielectric surface. Exposure to the first process condition and thesecond process condition is optionally repeated to form a desiredthickness of the AlOx etch stop layer.

Further embodiments of the disclosure are directed to processing methodscomprising positioning a substrate within a processing chamber, whereinthe substrate comprises a copper or tungsten surface and a dielectricsurface. The substrate is exposed to an aluminum precursor gascomprising dimethyl aluminum isopropoxide and to a reactant comprisingan alcohol to selectively form an aluminum oxide (AlOx) etch stop layerhaving a selectivity of at least about 5:1 onto the copper or tungstensurface. The dielectric surface is left exposed. A chemical vapordeposition process is used wherein a temperature of the substrate is400° C. or less.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 shows a cross-sectional view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 2 shows a partial perspective view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 3 shows a schematic view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 4 shows a schematic view of a portion of a wedge shaped gasdistribution assembly for use in a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 5 shows a schematic view of a batch processing chamber inaccordance with one or more embodiments of the disclosure;

FIG. 6 shows a schematic cross-sectional view of a substrate with anAlOx etch stop layer deposited on a metal surface in accordance with oneor more embodiments of the disclosure;

FIG. 7 shows a schematic cross-sectional view of a substrate with anAlOx etch stop layer deposited on a metal surface with other optionallayers in accordance with one or more embodiments of the disclosure;

FIG. 8 is a graph of atomic % versus etch time for AlOx film selectivelyformed on copper;

FIG. 9 is a Transmission Electron Microscope (TEM) image of a dielectricsurface after formation of Al₂O₃ film on a copper surface;

FIG. 10 is a graph of atomic % versus etch time for AlOx filmselectively formed on tungsten at 390° C.

FIG. 11 is a Transmission Electron Microscope (TEM) image of adielectric surface after formation of Al₂O₃ film on a tungsten surface.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

Embodiments of the disclosure provide methods to deposit aluminum oxidelayers onto metal surfaces such as copper or cobalt or tungsten in thepresence of low-k dielectric material. An organic aluminum-containingprecursor is used, preferably an isopropoxide based aluminum precursor.Methods of deposition may include: thermal decomposition, PECVD, andALD. With thermal decomposition, temperature of the substrate is >450°C.; no oxidation of metal surface without any selectivity relative todielectric surfaces. With PECVD, the temperature of the substrateis >200° C.; very minimal oxidation of metal with no selectivityrelative to dielectric surfaces. With ALD in the presence of oxygen at<300° C., selective deposition of film is obtained, but oxidation ofmetal surface may be expected. With ALD in the presence of alcohol at<400° C., there is selectivity and minimal oxidation of metal (Cu, W,and Co).

Upon use of an organic aluminum precursor, a carbon impurity may bepresent. Advantages of the deposited AlOx film with carbon as impurityinclude having etch selectivity between the film and low-K dielectricmaterial used in back end metallization. Another advantage is minimaldamage of the low-k material and change of its properties and barrierproperties to oxidation, moisture and Cu diffusion. The depositionprocess also minimizes or eliminates the oxidation of the underlyingmetal film.

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOl), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal and/or bake the substratesurface. In addition to film processing directly on the surface of thesubstrate itself, in the present disclosure, any of the film processingsteps disclosed may also be performed on an underlayer formed on thesubstrate as disclosed in more detail below, and the term “substratesurface” is intended to include such underlayer as the contextindicates. Thus for example, where a film/layer or partial film/layerhas been deposited onto a substrate surface, the exposed surface of thenewly deposited film/layer becomes the substrate surface.

Embodiments of the disclosure provide processing methods to providealuminum oxide etch stop layers. As used in this specification and theappended claims, the terms “selective deposition of” and “selectivelyforming” a film on one surface over another surface, and the like, meansthat a first amount of the film is deposited on the first surface and asecond amount of film is deposited on the second surface, where thesecond amount of film is less than the first amount of film or none. Theterm “over” used in this regard does not imply a physical orientation ofone surface on top of another surface, rather a relationship of thethermodynamic or kinetic properties of the chemical reaction with onesurface relative to the other surface. For example, selectivelydepositing an aluminum oxide layer onto a metal surface over adielectric surface means that the aluminum oxide deposits on the mealsurface and less aluminum oxide deposits on the dielectric surface; orthat the formation of the aluminum oxide on the meal surface isthermodynamically or kinetically favorable relative to the formation ofaluminum oxide on the dielectric surface. Stated differently, the filmcan be selectively deposited onto a first surface relative to a secondsurface means that deposition on the first surface is favorable relativeto the deposition on the second surface.

According to one or more embodiments, the method uses a chemical vapordeposition (CVD) process. In such embodiments, the substrate surface isexposed to a first reactive gas and a second reactive gas at the sametime so that the first reactive gas and the second reactive gas mixduring formation of the film.

According to one or more embodiments, the method uses an atomic layerdeposition (ALD) process. In such embodiments, the substrate surface isexposed to the precursors (or reactive gases) sequentially orsubstantially sequentially. As used herein throughout the specification,“substantially sequentially” means that a majority of the duration of aprecursor exposure does not overlap with the exposure to a co-reactant,although there may be some overlap. As used in this specification andthe appended claims, the terms “precursor”, “reactant”, “reactive gas”and the like are used interchangeably to refer to any gaseous speciesthat can react with the substrate surface, or a species present on thesubstrate surface.

In one or more embodiments, the method is performed using an AtomicLayer Deposition (ALD) process. An ALD process is a self-limitingprocess where a single layer of material is deposited using a binary (orhigher order) reaction. An individual ALD reaction is theoreticallyself-limiting continuing until all available active sites on thesubstrate surface have been reacted. ALD processes can be performed bytime-domain or spatial ALD.

In a time-domain process, the processing chamber and substrate areexposed to a single reactive gas at any given time. In an exemplarytime-domain process, the processing chamber might be filled with a metalprecursor for a time to allow the metal precursor to fully react withthe available sites on the substrate. The processing chamber can then bepurged of the precursor before flowing a second reactive gas into theprocessing chamber and allowing the second reactive gas to fully reactwith the substrate surface or material on the substrate surface. Thetime-domain process minimizes the mixing of reactive gases by ensuringthat only one reactive gas is present in the processing chamber at anygiven time. At the beginning of any reactive gas exposure, there is adelay in which the concentration of the reactive species goes from zeroto the final predetermined pressure. Similarly, there is a delay inpurging all of the reactive species from the process chamber.

In a spatial ALD process, the substrate is moved between differentprocess regions within a single processing chamber. Each of theindividual process regions is separated from adjacent process regions bya gas curtain. The gas curtain helps prevent mixing of the reactivegases to minimize any gas phase reactions. Movement of the substratethrough the different process regions allows the substrate to besequentially exposed to the different reactive gases while preventinggas phase reactions.

Some embodiments of the disclosure are directed to film depositionprocesses using a batch processing chamber, also referred to as aspatial processing chamber. FIG. 1 shows a cross-section of a processingchamber 100 including a gas distribution assembly 120, also referred toas injectors or an injector assembly, and a susceptor assembly 140. Thegas distribution assembly is any type of gas delivery device used in aprocessing chamber. The gas distribution assembly 120 includes a frontsurface 121 which faces the susceptor assembly 140. The front surface121 can have any number or variety of openings to deliver a flow ofgases toward the susceptor assembly 140. The gas distribution assembly120 also includes an outer peripheral edge 124 which in the embodimentsshown, is substantially round.

The specific type of gas distribution assembly 120 used can varydepending on the particular process being used. Embodiments of thedisclosure can be used with any type of processing system where the gapbetween the susceptor and the gas distribution assembly is controlled.In a binary reaction, the plurality of gas channels can include at leastone first reactive gas A channel, at least one second reactive gas Bchannel, at least one purge gas P channel and/or at least one vacuum Vchannel. The gases flowing from the first reactive gas A channel(s), thesecond reactive gas B channel(s) and the purge gas P channel(s) aredirected toward the top surface of the wafer. Some of the gas flow moveshorizontally across the surface of the wafer and out of the processingregion through the purge gas P channel(s).

In some embodiments, the gas distribution assembly 120 is a rigidstationary body made of a single injector unit. In one or moreembodiments, the gas distribution assembly 120 is made up of a pluralityof individual sectors (e.g., injector units 122), as shown in FIG. 2.Either a single piece body or a multi-sector body can be used with thevarious embodiments of the disclosure described.

A susceptor assembly 140 is positioned beneath the gas distributionassembly 120. The susceptor assembly 140 includes a top surface 141 andat least one recess 142 in the top surface 141. The susceptor assembly140 also has a bottom surface 143 and an edge 144. The recess 142 can beany suitable shape and size depending on the shape and size of thesubstrates 60 being processed. In the embodiment shown in FIG. 1, therecess 142 has a flat bottom to support the bottom of the wafer;however, the bottom of the recess can vary. In some embodiments, therecess has step regions around the outer peripheral edge of the recesswhich are sized to support the outer peripheral edge of the wafer. Theamount of the outer peripheral edge of the wafer that is supported bythe steps can vary depending on, for example, the thickness of the waferand the presence of features already present on the back side of thewafer.

In some embodiments, as shown in FIG. 1, the recess 142 in the topsurface 141 of the susceptor assembly 140 is sized so that a substrate60 supported in the recess 142 has a top surface 61 substantiallycoplanar with the top surface 141 of the susceptor 140. As used in thisspecification and the appended claims, the term “substantially coplanar”means that the top surface of the wafer and the top surface of thesusceptor assembly are coplanar within ±0.2 mm. In some embodiments, thetop surfaces are coplanar within ±0.15 mm, 0.10 mm or ±0.05 mm.

The susceptor assembly 140 of FIG. 1 includes a support post 160 whichis capable of lifting, lowering and rotating the susceptor assembly 140.The susceptor assembly may include a heater, or gas lines, or electricalcomponents within the center of the support post 160. The support post160 may be the primary means of increasing or decreasing the gap betweenthe susceptor assembly 140 and the gas distribution assembly 120, movingthe susceptor assembly 140 into proper position. The susceptor assembly140 may also include fine tuning actuators 162 which can makemicro-adjustments to susceptor assembly 140 to create a predeterminedgap 170 between the susceptor assembly 140 and the gas distributionassembly 120.

In some embodiments, the gap 170 distance is in the range of about 0.1mm to about 5.0 mm, or in the range of about 0.1 mm to about 3.0 mm, orin the range of about 0.1 mm to about 2.0 mm, or in the range of about0.2 mm to about 1.8 mm, or in the range of about 0.3 mm to about 1.7 mm,or in the range of about 0.4 mm to about 1.6 mm, or in the range ofabout 0.5 mm to about 1.5 mm, or in the range of about 0.6 mm to about1.4 mm, or in the range of about 0.7 mm to about 1.3 mm, or in the rangeof about 0.8 mm to about 1.2 mm, or in the range of about 0.9 mm toabout 1.1 mm, or about 1 mm.

The processing chamber 100 shown in the Figures is a carousel-typechamber in which the susceptor assembly 140 can hold a plurality ofsubstrates 60. As shown in FIG. 2, the gas distribution assembly 120 mayinclude a plurality of separate injector units 122, each injector unit122 being capable of depositing a film on the wafer, as the wafer ismoved beneath the injector unit. Two pie-shaped injector units 122 areshown positioned on approximately opposite sides of and above thesusceptor assembly 140. This number of injector units 122 is shown forillustrative purposes only. It will be understood that more or lessinjector units 122 can be included. In some embodiments, there are asufficient number of pie-shaped injector units 122 to form a shapeconforming to the shape of the susceptor assembly 140. In someembodiments, each of the individual pie-shaped injector units 122 may beindependently moved, removed and/or replaced without affecting any ofthe other injector units 122. For example, one segment may be raised topermit a robot to access the region between the susceptor assembly 140and gas distribution assembly 120 to load/unload substrates 60.

Processing chambers having multiple gas injectors can be used to processmultiple wafers simultaneously so that the wafers experience the sameprocess flow. For example, as shown in FIG. 3, the processing chamber100 has four gas injector assemblies and four substrates 60. At theoutset of processing, the substrates 60 can be positioned between theinjector assemblies 30. Rotating 17 the susceptor assembly 140 by 45°will result in each substrate 60 which is between gas distributionassemblies 120 to be moved to an gas distribution assembly 120 for filmdeposition, as illustrated by the dotted circle under the gasdistribution assemblies 120. An additional 45° rotation would move thesubstrates 60 away from the injector assemblies 30. The number ofsubstrates 60 and gas distribution assemblies 120 can be the same ordifferent. In some embodiments, there are the same numbers of wafersbeing processed as there are gas distribution assemblies. In one or moreembodiments, the number of wafers being processed are fraction of or aninteger multiple of the number of gas distribution assemblies. Forexample, if there are four gas distribution assemblies, there are 4×wafers being processed, where x is an integer value greater than orequal to one. In an exemplary embodiment, the gas distribution assembly120 includes eight processing regions separated by gas curtains and thesusceptor assembly 140 can hold six wafers.

The processing chamber 100 shown in FIG. 3 is merely representative ofone possible configuration and should not be taken as limiting the scopeof the disclosure. Here, the processing chamber 100 includes a pluralityof gas distribution assemblies 120. In the embodiment shown, there arefour gas distribution assemblies (also called injector assemblies 30)evenly spaced about the processing chamber 100. The processing chamber100 shown is octagonal; however, those skilled in the art willunderstand that this is one possible shape and should not be taken aslimiting the scope of the disclosure. The gas distribution assemblies120 shown are trapezoidal, but can be a single circular component ormade up of a plurality of pie-shaped segments, like that shown in FIG.2.

The embodiment shown in FIG. 3 includes a load lock chamber 180, or anauxiliary chamber like a buffer station. This load lock chamber 180 isconnected to a side of the processing chamber 100 to allow, for examplethe substrates (also referred to as substrates 60) to be loaded/unloadedfrom the processing chamber 100. A wafer robot may be positioned in theload lock chamber 180 to move the substrate onto the susceptor.

Rotation of the carousel (e.g., the susceptor assembly 140) can becontinuous or intermittent (discontinuous). In continuous processing,the wafers are constantly rotating so that they are exposed to each ofthe injectors in turn. In discontinuous processing, the wafers can bemoved to the injector region and stopped, and then to the region 84between the injectors and stopped. For example, the carousel can rotateso that the wafers move from an inter-injector region across theinjector (or stop adjacent the injector) and on to the nextinter-injector region where the carousel can pause again. Pausingbetween the injectors may provide time for additional processing betweeneach layer deposition (e.g., exposure to plasma).

FIG. 4 shows a sector or portion of a gas distribution assembly 220,which may be referred to as an injector unit 122. The injector units 122can be used individually or in combination with other injector units.For example, as shown in FIG. 5, four of the injector units 122 of FIG.4 are combined to form a single gas distribution assembly 220. (Thelines separating the four injector units are not shown for clarity.)While the injector unit 122 of FIG. 4 has both a first reactive gas port125 and a second gas port 135 in addition to purge gas ports and vacuumports 145, an injector unit 122 does not need all of these components.

Referring to both FIGS. 4 and 5, a gas distribution assembly 220 inaccordance with one or more embodiment may comprise a plurality ofsectors (or injector units 122) with each sector being identical ordifferent. The gas distribution assembly 220 is positioned within theprocessing chamber and comprises a plurality of elongate gas ports 125,135, 155 and elongate vacuum ports 145 in a front surface 121 of the gasdistribution assembly 220. The plurality of elongate gas ports 125, 135,155 and elongate vacuum ports 145 extend from an area adjacent the innerperipheral edge 123 toward an area adjacent the outer peripheral edge124 of the gas distribution assembly 220. The plurality of gas portsshown include a first reactive gas port 125, a second gas port 135, avacuum port 145 which surrounds each of the first reactive gas ports andthe second reactive gas ports and a purge gas port 155.

With reference to the embodiments shown in FIG. 4 or 5, when statingthat the ports extend from at least about an inner peripheral region toat least about an outer peripheral region, however, the ports can extendmore than just radially from inner to outer regions. The ports canextend tangentially as vacuum port 145 surrounds reactive gas port 125and reactive gas port 135. In the embodiment shown in FIGS. 4 and 5, thewedge shaped reactive gas ports 125, are surrounded on all edges,including adjacent the inner peripheral region and outer peripheralregion, by a vacuum port 145.

Referring to FIG. 4, as a substrate moves along path 127, each portionof the substrate surface is exposed to the various reactive gases. Tofollow the path 127, the substrate will be exposed to, or “see”, a purgegas port 155, a vacuum port 145, a first reactive gas port 125, a vacuumport 145, a purge gas port 155, a vacuum port 145, a second gas port 135and a vacuum port 145. Thus, at the end of the path 127 shown in FIG. 4,the substrate has been exposed to the first gas port 125 and the secondgas port 135 to form a layer. The injector unit 122 shown makes aquarter circle but could be larger or smaller. The gas distributionassembly 220 shown in FIG. 5 can be considered a combination of four ofthe injector units 122 of FIG. 4 connected in series. The injector unit122 of FIG. 4 shows a gas curtain 150 that separates the reactive gases.The term “gas curtain” is used to describe any combination of gas flowsor vacuum that separate reactive gases from mixing. The gas curtain 150shown in FIG. 4 comprises the portion of the vacuum port 145 next to thefirst reactive gas port 125, the purge gas port 155 in the middle and aportion of the vacuum port 145 next to the second gas port 135. Thiscombination of gas flow and vacuum can be used to prevent or minimizegas phase reactions of the first reactive gas and the second reactivegas.

Referring to FIG. 5, the combination of gas flows and vacuum from thegas distribution assembly 220 form a separation into a plurality ofprocessing regions 250. The processing regions are roughly definedaround the individual gas ports 125, 135 with the gas curtain 150between 250. The embodiment shown in FIG. 5 makes up eight separateprocessing regions 250 with eight separate gas curtains 150 between. Aprocessing chamber can have at least two processing region. In someembodiments, there are at least three, four, five, six, seven, eight,nine, 10, 11 or 12 processing regions.

During processing a substrate may be exposed to more than one processingregion 250 at any given time. However, the portions that are exposed tothe different processing regions will have a gas curtain separating thetwo. For example, if the leading edge of a substrate enters a processingregion including the second gas port 135, a middle portion of thesubstrate will be under a gas curtain 150 and the trailing edge of thesubstrate will be in a processing region including the first reactivegas port 125.

A factory interface 280, which can be, for example, a load lock chamber,is shown connected to the processing chamber 100. A substrate 60 isshown superimposed over the gas distribution assembly 220 to provide aframe of reference. The substrate 60 may often sit on a susceptorassembly to be held near the front surface 121 of the gas distributionassembly 120. The substrate is loaded via the factory interface 280 intothe processing chamber 100 onto a substrate support or susceptorassembly (see FIG. 3). The substrate 60 can be shown positioned within aprocessing region because the substrate is located adjacent the firstreactive gas port 125 and between two gas curtains 150 a, 150 b.Rotating the substrate 60 along path 127 will move the substratecounter-clockwise around the processing chamber 100. Thus, the substrate60 will be exposed to the first processing region 250 a through theeighth processing region 250 h, including all processing regionsbetween.

Embodiments of the disclosure are directed to processing methodscomprising a processing chamber 100 with a plurality of processingregions 250 a-250 h with each processing region separated from anadjacent region by a gas curtain 150. For example, the processingchamber shown in FIG. 5. The number of gas curtains and processingregions within the processing chamber can be any suitable numberdepending on the arrangement of gas flows. The embodiment shown in FIG.5 has eight gas curtains 150 and eight processing regions 250 a-250 h.The number of gas curtains is generally equal to or greater than thenumber of processing regions.

A plurality of substrates 60 are positioned on a substrate support, forexample, the susceptor assembly 140 shown FIGS. 1 and 2. The pluralityof substrates 60 are rotated around the processing regions forprocessing. Generally, the gas curtains 150 are engaged (gas flowing andvacuum on) throughout processing including periods when no reactive gasis flowing into the chamber.

A first reactive gas A is flowed into one or more of the processingregions 250 while an inert gas is flowed into any processing region 250which does not have a first reactive gas A flowing into it. For exampleif the first reactive gas is flowing into processing regions 250 bthrough processing region 250 h, an inert gas would be flowing intoprocessing region 250 a. The inert gas can be flowed through the firstreactive gas port 125 or the second gas port 135.

The inert gas flow within the processing regions can be constant orvaried. In some embodiments, the reactive gas is co-flowed with an inertgas. The inert gas will act as a carrier and diluent. Since the amountof reactive gas, relative to the carrier gas, is small, co-flowing maymake balancing the gas pressures between the processing regions easierby decreasing the differences in pressure between adjacent regions.

FIG. 6 is a schematic cross-sectional view of a substrate with an AlOxetch stop layer deposited on a metal surface (e.g., tungsten) inaccordance with one or more embodiments of the disclosure. A substrate300 containing dielectric layer 304 disposed over underlayer 302comprises a metal surface 314 of an interconnect 308 and a dielectricsurface 310. The substrate 300 is provided in a chemical vapordeposition chamber for processing. As used in this regard, the term“provided” means that the substrate is placed into a position orenvironment for further processing. In this embodiment, the interconnectmay be tungsten, which provides a tungsten surface. The AlOx etch stoplayer 316 is selectively deposited onto the metal surface 314 over thedielectric surface 310. In one or more embodiments, the selectivity maybe at least about 5:1 or in the range of about 5:1 to about 20:1 or atleast about 20:1.

Interconnects 308 are disposed within dielectric layer 304 and areseparated from dielectric layer 304 by barrier layer 306. Dielectriclayer 304 contains a dielectric material, such as a low-k dielectricmaterial. In one example, dielectric layer 304 contains a low-kdielectric material, such as a silicon carbide oxide material or acarbon doped silicon oxide material, for example, BLACK DIAMOND® IIlow-k dielectric material, available from Applied Materials, Inc.,located in Santa Clara, Calif.

Barrier layer 306 may be conformally deposited into the aperture withindielectric layer 304. Barrier layer 306 may be formed or deposited by aPVD process, an ALD, or a CVD process, and may have a thickness within arange from about 5 Å to about 50 Å, preferably, from about 10 Å to about30 Å. Barrier layer 306 may contain titanium, titanium nitride,tantalum, tantalum nitride, tungsten, tungsten nitride, derivativesthereof, or combinations thereof. In some embodiments, barrier layer 306may contain a tantalum/tantalum nitride bilayer or titanium/titaniumnitride bilayer.

FIG. 7 is a schematic cross-sectional view of a substrate with an AlOxetch stop layer deposited on a metal surface with other optional layersin accordance with one or more embodiments of the disclosure. Asubstrate 400 containing dielectric layer 404 disposed over underlayer402 comprises a metal surface 414 of an interconnect 408 and adielectric surface 410. The substrate is provided in a chemical vapordeposition chamber for processing. In this embodiment, the interconnectmay be copper, which provides a copper surface. The metal surface 414may have a selectively formed capping layer 418, which comprises cobalt.The AlOx etch stop layer 416 is selectively deposited onto the metalsurface 414 including the capping layer 418 over the dielectric surface410. In one or more embodiments, the selectivity may be at least about5:1 or in the range of about 5:1 to about 20:1 or at least about 20:1.

Optional SiOC layer may be formed onto the AlOx etch stop layer infurther processing.

Interconnects 408 are disposed within dielectric layer 404 and areseparated from dielectric layer 404 by barrier layer 406. Dielectriclayer 404 like dielectric layer 304 discussed above contains adielectric material, such as a low-k dielectric material. In oneexample, dielectric layer 404 contains a low-k dielectric material, suchas a silicon carbide oxide material or a carbon doped silicon oxidematerial, for example, BLACK DIAMOND® II low-k dielectric material,available from Applied Materials, Inc., located in Santa Clara, Calif.

Barrier layer 406 may be conformally deposited into the aperture withindielectric layer 404. Barrier layer 406 may be formed or deposited by aPVD process, an ALD, or a CVD process, and may have a thickness within arange from about 5 Å to about 50 Å, preferably, from about 10 Å to about30 Å. Barrier layer 306 may contain titanium, titanium nitride,tantalum, tantalum nitride, tungsten, tungsten nitride, derivativesthereof, or combinations thereof. In some embodiments, barrier layer 406may contain a tantalum/tantalum nitride bilayer or titanium/titaniumnitride bilayer.

In some embodiments, as shown in FIGS. 7-8, the metal surface and thedielectric surface are substantially coplanar. Those skilled in the artwill understand that substantially coplanar means that the major planesformed by individual surface are within about the same plane. As used inthis regard, “substantially coplanar” means that the plane formed by thefirst surface is within ±100 μm of the plane formed by the secondsurface, measured at the boundary between the first surface and thesecond surface. In some embodiments, the planes formed by the firstsurface and the second surface are within ±500 μm, ±400 μm, ±300 μm,±200 μm, ±100 μm, ±50 μm, ±10 μm, ±5 μm, ±1μm, ±500 nm, ±250 nm, ±100nm, ±50 nm, ±10 nm, ±1 nm or ±0.1 nm.

The AlOx layer formed can be any suitable film. In some embodiments, thefilm formed is an amorphous or crystalline aluminum-containing filmcomprising one or more species according to AIOx, where the formula isrepresentative of the atomic composition, not stoichiometric. The filmcan be formed by any suitable process including, but not limited to,chemical vapor deposition (CVD), plasma-enhanced chemical vapordeposition (PECVD), atomic layer deposition (ALD), and plasma-enhancedatomic layer deposition (PEALD). Precursors of aluminum may beisopropoxide-based precursors. For example, the aluminum precursor maycomprise dimethyl aluminum isopropoxide. The precursor may be heated ina hot can to increase the vapor pressure and be delivered to the chamberusing a carrier gas (e.g., ultrahigh purity (UHP) Ar, He, H₂, N2, etc.).

The reactant may comprise an oxygen source. The reactant may be selectedfrom the group consisting of: O₂, O₂ plasma, H₂O, H₂O plasma, D₂O, O₃,methanol, ethanol, isopropanol. Preferably, the reactant isnon-oxidizing. As used herein, a non-oxidizing reactant is one that doesnot donate oxygen to the metal surface. Preferred non-oxidizingreactants are: alcohols such as methanol, ethanol, and/or isopropanoland ketones such as methyl isobutyl ketone (MIBK).

In some embodiments, the AlOx etch stop layer 316 or 416 is a continuousfilm. As used herein, the term “continuous” refers to a layer thatcovers an entire exposed surface without gaps or bare spots that revealmaterial underlying the deposited layer. A continuous layer may havegaps or bare spots with a surface area less than about 1% of the totalsurface area of the film. The etch stop layer may have a carbon impuritypresent. Carbon content may be less than about 10% or 5% or 1% or 0.5%or 0.1% carbon on an atomic basis in the film.

The temperature of the substrate during deposition can be any suitabletemperature depending on, for example, the precursor(s) being used. Insome embodiments, the deposition temperature is in the range of about50° C. to less than 400° C., or in the range of about 200° C. to about390° C., or in the range of about 250° C. to about 280° C. Thedeposition can occur with or without plasma. For a PECVD process, plasmamay be used with alumina precursor and no reactant gases in the presenceof noble gases. For ALD or thermal deposition process there generally isno plasma. For processes using plasma, the plasma can be acapacitively-coupled plasma (CCP) or inductively coupled plasma (ICP) ormicrowaves and can be a direct plasma or a remote plasma. Plasma powerfor CCP plasma may be in the range of 20 to 400 W. The processingchamber pressure during deposition can be in the range of about 50 mTorrto 750 Torr, or in the range of about 100 mTorr to about 400 Torr, or inthe range of about 1 Torr to about 100 Torr, or in the range of about 2Torr to about 10 Torr. Post deposition, plasma treatment with Ar orAr/O₂ mixture may be done to improve film property such as film density.

According to one or more embodiments, the substrate is subjected toprocessing prior to and/or after forming the etch stop layer. Thisprocessing can be performed in the same chamber or in one or moreseparate processing chambers. In some embodiments, the substrate ismoved from the first chamber to a separate, second chamber for furtherprocessing. The substrate can be moved directly from the first chamberto the separate processing chamber, or it can be moved from the firstchamber to one or more transfer chambers, and then moved to the separateprocessing chamber. Accordingly, the processing apparatus may comprisemultiple chambers in communication with a transfer station. An apparatusof this sort may be referred to as a “cluster tool” or “clusteredsystem,” and the like.

Generally, a cluster tool is a modular system comprising multiplechambers which perform various functions including substratecenter-finding and orientation, degassing, annealing, deposition and/oretching. According to one or more embodiments, a cluster tool includesat least a first chamber and a central transfer chamber. The centraltransfer chamber may house a robot that can shuttle substrates betweenand among processing chambers and load lock chambers. The transferchamber is typically maintained at a vacuum condition and provides anintermediate stage for shuttling substrates from one chamber to anotherand/or to a load lock chamber positioned at a front end of the clustertool. Two well-known cluster tools which may be adapted for the presentdisclosure are the Centura® and the Endura®, both available from AppliedMaterials, Inc., of Santa Clara, Calif. However, the exact arrangementand combination of chambers may be altered for purposes of performingspecific steps of a process as described herein. Other processingchambers which may be used include, but are not limited to, cyclicallayer deposition (CLD), atomic layer deposition (ALD), chemical vapordeposition (CVD), physical vapor deposition (PVD), etch, pre-clean,chemical clean, thermal treatment such as RTP, plasma nitridation,degas, orientation, hydroxylation and other substrate processes. Bycarrying out processes in a chamber on a cluster tool, surfacecontamination of the substrate with atmospheric impurities can beavoided without oxidation prior to depositing a subsequent film.

According to one or more embodiments, the substrate is continuouslyunder vacuum or “load lock” conditions, and is not exposed to ambientair when being moved from one chamber to the next. The transfer chambersare thus under vacuum and are “pumped down” under vacuum pressure. Inertgases may be present in the processing chambers or the transferchambers. In some embodiments, an inert gas is used as a purge gas toremove some or all of the reactants. According to one or moreembodiments, a purge gas is injected at the exit of the depositionchamber to prevent reactants from moving from the deposition chamber tothe transfer chamber and/or additional processing chamber. Thus, theflow of inert gas forms a curtain at the exit of the chamber.

The substrate can be processed in single substrate deposition chambers,where a single substrate is loaded, processed and unloaded beforeanother substrate is processed. The substrate can also be processed in acontinuous manner, similar to a conveyer system, in which multiplesubstrate are individually loaded into a first part of the chamber, movethrough the chamber and are unloaded from a second part of the chamber.The shape of the chamber and associated conveyer system can form astraight path or curved path. Additionally, the processing chamber maybe a carousel in which multiple substrates are moved about a centralaxis and are exposed to deposition, etch, annealing, cleaning, etc.processes throughout the carousel path.

During processing, the substrate can be heated or cooled. Such heatingor cooling can be accomplished by any suitable means including, but notlimited to, changing the temperature of the substrate support andflowing heated or cooled gases to the substrate surface. In someembodiments, the substrate support includes a heater/cooler which can becontrolled to change the substrate temperature conductively. In one ormore embodiments, the gases (either reactive gases or inert gases) beingemployed are heated or cooled to locally change the substratetemperature. In some embodiments, a heater/cooler is positioned withinthe chamber adjacent the substrate surface to convectively change thesubstrate temperature.

The substrate can also be stationary or rotated during processing. Arotating substrate can be rotated continuously or in discrete steps. Forexample, a substrate may be rotated throughout the entire process, orthe substrate can be rotated by a small amount between exposures todifferent reactive or purge gases. Rotating the substrate duringprocessing (either continuously or in steps) may help produce a moreuniform deposition or etch by minimizing the effect of, for example,local variability in gas flow geometries.

In atomic layer deposition type chambers, the substrate can be exposedto the first and second precursors either spatially or temporallyseparated processes. Temporal ALD is a traditional process in which thefirst precursor flows into the chamber to react with the surface. Thefirst precursor is purged from the chamber before flowing the secondprecursor. In spatial ALD, both the first and second precursors aresimultaneously flowed to the chamber but are separated spatially so thatthere is a region between the flows that prevents mixing of theprecursors. In spatial ALD, the substrate is moved relative to the gasdistribution plate, or vice-versa.

In embodiments, where one or more of the parts of the methods takesplace in one chamber, the process may be a spatial ALD process. Althoughone or more of the chemistries described above may not be compatible(i.e., result in reaction other than on the substrate surface and/ordeposit on the chamber), spatial separation ensures that the reagentsare not exposed to each in the gas phase. For example, temporal ALDinvolves the purging the deposition chamber. However, in practice it issometimes not possible to purge all of the excess reagent out of thechamber before flowing in additional regent. Therefore, any leftoverreagent in the chamber may react. With spatial separation, excessreagent does not need to be purged, and cross-contamination is limited.Furthermore, a lot of time can be taken to purge a chamber, andtherefore throughput can be increased by eliminating the purge step.

EXAMPLES Example 1

AlOx layer was selectively deposited onto a copper surface in thepresence of TiN and SiO₂ dielectric surfaces by an ALD process usingdimethyl aluminum isopropoxide and oxygen at a substrate temperature ofbelow 300° C. The results are in Table 1, showing layer thicknessrelative to # of cycles.

TABLE 1 Surface 10 cycles 30 cycles 50 cycles 100 cycles TiN 0  0 0  0  None detected None detected None detected None detected Cu 135 Å 190 Å250 Å 290 Å SiO₂ 0  10 Å  20 Å  42 Å None detected Selectivity ∞ 19 12.56.9 Cu:SiO₂

FIG. 8 is a graph of atomic % versus etch time for the AlOx layerselectively formed on copper, where there is no carbon present in thelayer.

Example 2

AlOx layer was selectively deposited onto a copper surface (located onTa and Si) in the presence of a SiO₂ dielectric surface by an ALDprocess using dimethyl aluminum isopropoxide and ethyl alcohol at asubstrate temperature of 250° C. The ALD process includes: 50 cycles, 5torr chamber pressure, 5 seconds precursor/10 seconds purge/15 secondsalcohol/10 seconds purge. With ethyl alcohol as reactant the Cu surfacedoes not get oxidized. No deposition on silcon dioxide surface wasobserved for this condition. FIG. 9 is a Transmission ElectronMicroscope (TEM) images of a dielectric surface after formation of Al₂O₃film.

Example 3

AlOx layer was selectively deposited onto a tungsten surface in thepresence of SiO₂ dielectric surface by an ALD process using dimethylaluminum isopropoxide and ethyl alcohol at substrate temperatures of250° C. and 390° C. The ALD process includes: 50 cycles, 5 torr chamberpressure, 5 seconds precursor/10 seconds purge/15 seconds alcohol/10seconds purge. The W surface was not treated to remove oxides. Withethyl alcohol as reactant the W surface does not get further oxidized.FIG. 10 is a Transmission Electron Microscope (TEM) images of adielectric surface after formation of Al₂O₃ film 390° C. At 390° C., 55Aof Al₂O₃ film was deposited on W surface and 8 Å was formed on SiO₂surface. At 390° C., Al₂O₃ film was deposited on W surface based onX-ray photoelectron spectroscopy (XPS) and energy-dispersive X-rayspectroscopy (EDX) data.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A processing method comprising: positioning asubstrate within a processing chamber, wherein the substrate comprises ametal surface and a dielectric surface; exposing the substrate to afirst process condition comprising an aluminum precursor gas comprisingan isopropoxide based aluminum precursor; exposing the substrate to asecond process condition comprising an oxygen source reactant toselectively form an aluminum oxide (AlOx) etch stop layer onto the metalsurface while leaving exposed the dielectric surface; and optionallyrepeating exposure to the first process condition and the second processcondition to form a desired thickness of the AlOx etch stop layer. 2.The processing method of claim 1, wherein the isopropoxide basedaluminum precursor comprises dimethyl aluminum isopropoxide.
 3. Theprocessing method of claim 1, wherein the dielectric surface comprisessilicon.
 4. The processing method of claim 1, wherein the substrate isat a temperature of less than 400° C.
 5. The processing method of claim1, wherein the reactant is non-oxidizing to the metal surface.
 6. Theprocessing method of claim 5, wherein the reactant comprises an alcohol.7. A processing method comprising: positioning a substrate within aprocessing chamber, wherein the substrate comprises a copper or tungstensurface and a dielectric surface; and exposing the substrate to a firstprocess condition comprising an aluminum precursor gas comprisingdimethyl aluminum isopropoxide; exposing the substrate to a secondprocess condition comprising an alcohol reactant to selectively form analuminum oxide (AlOx) etch stop layer having a selectivity of at leastabout 5:1 onto the copper or tungsten surface while leaving exposed thedielectric surface; and optionally repeating exposure to the firstprocess condition and the second process condition to form a desiredthickness of the aluminum oxide etch stop layer.
 8. The processingmethod of claim 7, wherein during the process a temperature of thesubstrate is 400° C. or less.
 9. The processing method of claim 7,wherein the process is an atomic layer deposition (ALD) process.
 10. Theprocessing method of claim 7, further comprising forming a SiOC layeronto the AlOx etch stop layer.
 11. The processing method of claim 7,wherein the alcohol comprises ethanol.
 12. The processing method ofclaim 7, wherein the AlOx etch stop layer comprises less than 10% carbonon an atomic basis.
 13. The processing method of claim 7, wherein thedielectric surface comprises silicon.